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Ludwig, F.

   
Paper Title Page
TUPCH025 Precision RF Gun Phase Monitor System for the VUV-FEL 1052
 
  • H. Schlarb, N. Heidbrook, H. Kapitza, F. Ludwig, N. Nagad
    DESY, Hamburg
 
  For RF photo-injectors, the properties of the high brightness beam critically depend on the synchronization between the RF gun acceleration phase and the photo-cathode laser. At the VUV-FEL, the phase stability is determined by operating the RF gun close to zero-crossing RF phase. This allows the conversion of phase variations into charge variations which then is readout by a precision charge measurement system based on toroids. In this paper, we discuss the limitation of this method. Resolution reduction of the charge measurement system due to electro-magnetic-interference is discussed in detail.  
TUPCH028 Layout of the Optical Synchronization System for FLASH 1061
 
  • A. Winter, P. Schmüser, A. Winter
    Uni HH, Hamburg
  • F. Loehl, F. Ludwig, H. Schlarb, B. Schmidt
    DESY, Hamburg
 
  The present RF synchronization system of the VUV-FEL can typically stabilize the arrival time of the electron bunches at the undulator to about 200 fs on a timescale of minutes and to several picoseconds on a timescale of hours. To improve the machine stability and to ensure optimal performance for the VUV-FEL user facility, a new ultra-precise timing system is mandatory. The optical synchronization system under construction will satisfy three goals: Firstly, it provides a local oscillator frequency with the same stability as the existing low-level RF regulation, secondly, it can synchronize the experimental lasers of the FEL users with a precision in the order of 30 fs, thirdly, it provides an ultra-stable reference for beam arrival time measurements and enables a feedback on the electron beam to compensate residual drifts and timing jitter. The optical synchronization system is based on an optical pulse train from a mode-locked laser with a highly stabilized repetition rate. This paper describes the proposed layout of the optical synchronization system, the integration into the machine layout and the diagnostic experiments to monitor the performance of the system.  
TUPCH029 High-precision Laser Master Oscillators for Optical Timing Distribution Systems in Future Light Sources 1064
 
  • A. Winter, P. Schmüser, A. Winter
    Uni HH, Hamburg
  • J. Chen, F.X. Kaertner
    MIT, Cambridge, Massachusetts
  • F.O. Ilday
    Bilkent University, Bilkent, Ankara
  • F. Ludwig, H. Schlarb
    DESY, Hamburg
 
  X-ray pulses with a pulse duration in the 10 fs regime or even less are needed for numerous experiments planned at next generation free electron lasers. A synchronization of probe laser pulses to the x-ray pulses with a stability on the order of the pulse width is highly desirable for these experiments. This requirement can be fulfilled by distributing an ultra-stable timing signal to various subsystems of the machine and to the experimental area to provide synchronization at the fs level over distances of several kilometers. Mode-locked fiber lasers serve as laser master oscillators (LMO), generating the frequencies required in the machine. The pulse train is distributed through length-stabilized fiber links. This paper focuses on the LMO, devoting special attention to the phase noise properties of the frequencies to be generated, its reliability to operate in an accelerator environment, and the residual timing jitter and drifts of the RF feedback for the fiber links. A prototype experimental system has been constructed and tested in an accelerator environment and its performance characteristics will be evaluated.  
TUPCH188 Phase Stability of the Next Generation RF Field Control for VUV- and X-ray Free Electron Laser 1453
 
  • F. Ludwig, M. Hoffmann, H. Schlarb, S. Simrock
    DESY, Hamburg
 
  For pump and probe experiments at VUV- and X-ray free electron lasers the stability of the electron beam and timing reference must be guaranteed in phase for the injector and bunch compression section within a resolution of 0.01 degree (rms) and in amplitude within 1 10-4 (rms). The performance of the field detection and regulation of the acceleration RF directly influences the phase and amplitude stability. In this paper we present the phase noise budget for a RF-regulation system including the noise characterization of all subcomponents, in detail down-converter, ADC sampling, vector-modulator, master oscillator and klystron. We study the amplitude to phase noise conversion for a detuned cavity. In addition we investigate the beam jitter induced by these noise sources within the regulation and determine the optimal controller gain. We acknowledge financial support by DESY Hamburg and the EUROFEL project.  
TUPCH191 Considerations for the Choice of the Intermediate Frequency and Sampling Rate for Digital RF Control 1462
 
  • S. Simrock, M. Hoffmann, F. Ludwig
    DESY, Hamburg
  • M.K. Grecki, T. Jezynski
    TUL-DMCS, Lodz
 
  Modern FPGA-based rf control systems employ digital field detectors where an intermediate frequency (IF) in the range of 10 to more than 100 MHz is sampled with a synchronized clock. Present ADC technology with 14-16 bit resolution allows for maximum sampling rates up to 250 MHz. While higher IF's increase the sensitivity to clock jitter, lower IF frequencies are more susceptible to electromagnetic noise. The choice of intermediate frequency and sampling rate should minimize the overall detector noise, provide high measurement bandwidth and low latency in field detection, and support algorithms for optimal field estimation.  
THOPA03 An Integrated Femtosecond Timing Distribution System for XFELs 2744
 
  • J. Kim, J. Burnham, dc. Cheever, J. Chen, F.X. Kaertner
    MIT, Cambridge, Massachusetts
  • M. Ferianis
    ELETTRA, Basovizza, Trieste
  • F.O. Ilday
    Bilkent University, Bilkent, Ankara
  • F. Ludwig, H. Schlarb, A. Winter
    DESY, Hamburg
 
  Tightly synchronized lasers and rf-systems with timing jitter in the few femtoseconds range are an important component of future x-ray free electron laser facilities. In this paper, we present an optical-rf phase detector that is capable of extracting an rf-signal from an optical pulse stream without amplitude-to-phase conversion. Extraction of a microwave signal with less than 10 fs timing jitter (from 1 Hz to 10 MHz) from an optical pulse stream is demonstrated. Scaling of this component to sub-femtosecond resolution is discussed. Together with low noise mode-locked lasers, timing-stabilized optical fiber links and compact optical cross-correlators, a flexible femtosecond timing distribution system with potentially sub-10 fs precision over distances of a few kilometres can be constructed. Experimental results on both synchronized rf and laser sources will be presented.

*A. Winter et al. "Synchronization of Femtosecond Pulses", Proceedings of FEL 2005.**J. Kim et al. "Large-Scale Timing Distribution and RF-Synchronization for FEL Facilities", Proc. of FEL 2004.

 
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THPPA01 High-precision Laser Master Oscillators for Optical Timing Distribution Systems in Future Light Sources 2747
 
  • A. Winter, P. Schmüser, A. Winter
    Uni HH, Hamburg
  • J. Chen, F.X. Kaertner
    MIT, Cambridge, Massachusetts
  • F.O. Ilday
    Bilkent University, Bilkent, Ankara
  • F. Ludwig, H. Schlarb
    DESY, Hamburg
 
  Abstract to be supplied  
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THOBFI01 A Sub 100 fs Electron Bunch Arrival-time Monitor System for FLASH 2781
 
  • F. Loehl, K.E. Hacker, F. Ludwig, H. Schlarb, B. Schmidt
    DESY, Hamburg
  • A. Winter
    Uni HH, Hamburg
 
  The stability of free-electron lasers and experiments carried out in pump-probe configurations depends sensitively on precise synchronization between the photo-injector laser, low-level RF-systems, probe lasers, and other components in the FEL. A measurement of the jitter in the arrival-time of the electron bunch with respect to the clock signal of a master oscillator is, therefore, of special importance. For this task, we propose an arrival-time monitor based on a beam pick-up with more than 10GHz bandwidth which permits measurements in the sub 100 fs regime. The RF-signal from the beam pick-up is sampled by an ultra-short laser pulse using a broad-band electro-optical modulator. The modulator converts the electron bunch arrival-time jitter into an amplitude modulation of the laser pulse. This modulation is detected by a photo detector and sampled by a fast ADC. By directly using the laser pulses from the master laser oscillator of the machine, any additional timing jitter is avoided. In this paper we present the layout of the system and first experimental results.  
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